1. Field of the Invention
The present invention relates to colored resinous articles with lurking metallic luster and to a process for manufacturing same. More particularly, the present invention relates to colored resinous articles with a concealed tone of metallic luster comprised of resinous moldings as the substrate overlaid successively with a base coat, a very thin metal film and a protective top coat as well as a process for the manufacture of such colored resinous articles wherein a material having a desired color tint is previously incorporated into either of the substrate or the base coat and the substrate is overlaid successively with the base coat, the thin metal film and the top coat by a method known per se.
2. Description of the Prior Arts
Heretofore, lustrously metallized resinous products are known which are manufactured by metallizing treatments of various resinous moldings. For example, U.S. Pat. No. 4,369,225 discloses flexible lustrously metallized resinous moldings manufactured by applying a base coat, a metal film and a protective top coat onto flexible resinous moldings. Such metallized resinous products possess brilliant metallic luster and flexibility inherent to resinous materials and thus are useful as ornaments in lieu of metallic products. All of these metallized products are of brilliant metallic appearance but those having a desired color with a concealed tone of metallic luster have not yet been proposed.
In recent years, there is an increasing demand of colored resinous articles having a concealed tone of metallic luster with the design of imparting a deeply noble feeling and new aesthetic value in appearance to resinous parts of motor vehicles. For realizing such demand it is necessary to impart a concealed tone of metallic luster in place of brilliant metallic luster while retaining the original color tint of the colored resinous articles. From the past, a dry plating method such as vacuum evaporation, sputtering or ion plating is known as a means for imparting metallic luster to resinous articles. However, the application of such a known dry plating method to the above incurs various undesirable results; the weather-resistance of the product becomes poor and considerable degradation takes place in the resinous article and the base coat so that the appearance of the product will be damaged by significant discoloration or fading of the colored resinous article. According to the known metallizing treatments adopting such dry plating method, the thickness of the metal film formed exceeds 400-500 .ANG. so that the resinous article is completely covered with the plated metal film, thus giving only metallic feeling in appearance. In the prior art methods, therefore, there was no technical concept of manufacturing metallized resinous articles as contemplated in the present invention, which show a deeply noble feeling in appearance by a concealed tone of metallic luster with the original tint of the colored resinous article or the base coat. Further, the conventional metallized products obtained according to the dry plating method tend to permit the formation of cracks on the metal film formed. Thus, the base coat has to be cured quickly to prevent the formation of cracks on the metal film. Even if a two-component polyurethane paint is used as the base coat, therefore, a yellowing type such as tolylene diisocyanate is actually used which permits rapid curing.
The metallized resinous articles obtained according to the conventional dry plating method find wide utility as outdoor ornamental parts of motor-vehicles. In case the articles with a metal film as thick as 400-500 .ANG. or more are irradiated with sun light, harmful UV-rays are almost reflected by such relatively thick metal film. Thus, there is no or a little demand for weather-resisting property for the base coat paint.
If the metal film in the metallized articles is as thin as 20-300 .ANG., UV-rays in sun light easily penetrate into the base coat or the molded article as substrate through such a thin metal film. Thus, weather-resistance is needed for the base coat and even for the substrate. Anyway, all of the conventional metallized resin articles show metallic feeling in appearance but no technical research has yet been reported hitherto for manufacturing metallized resinous articles showing a deeply noble feeling by their a concealed tone of metallic luster with the original color tint of the resinous material.
Recently, there arises a great demand for developing a new type of metallized resinous articles with a deeply noble feeling in the field of automobile industry with a view to improving ornamental or aesthetic value in appearance of the metallized resinous articles.